For the proposed concept of RIS-aided cell-free network, only the weighted sum-rate maximization is considered in this paper, while some other important performance metrics such as the energy efficiency [1]}, BS transmit power [2]}, user sinr [3]}, [4]}, and secrecy rate [5]} are left for future works. Moreover, since the perfectly known CSI is assumed in this paper, the challenging problem of channel estimation [6]} should be studied. In addition, the fully digital precoding at the BSs is considered in this paper, while the more energy-efficient hybrid precoding [7]} can be investigated in future works.
